The described technology relates generally to navigation systems and particularly to a navigation system for an airplane taxiing at an airport.
When an airplane lands at an airport, the ground control personnel for that airport provide a taxi clearance to the crewmembers of the airplane. The taxi clearance specifies a taxi route that the airplane is to use in taxiing from the runway, to the destination gate. Ground control personnel select a taxi clearance that facilitates taxiing from the landing runway to the destination gate or from the departing gate to the takeoff runway, that reduces congestion on the taxiways, and enhances safety. The ground control personnel radio the taxi route to the crewmembers, providing the names of the taxiways of the cleared taxi route. The names of the taxiways typically consist of one or two letters followed by an optional number. Example names of taxiways at an airport may be “A1,” “A2,” “E1,” “E2,” and “WC.” The ground control personnel may identify a taxi route by saying “echo two alpha one charlie three.” A crewmember may write down the names of the taxiways and then use those taxiways to taxi the airplane to the gate. Each taxiway is identified by one or more signs marked with its respective name. While taxiing, a crewmember can compare the names on the signs with the written-down names.
It is, of course, important for an airplane to follow its cleared taxi route. The typical taxiing process is, however, subject to human error. For example, a crewmember may incorrectly hear the name of a taxiway or may incorrectly write down the name of a taxiway. In addition, since adverse weather conditions may affect the visibility of the names of the taxiways on the signs, a crewmember may incorrectly identify a taxiway. As a result of these errors, a crewmember may inadvertently taxi the airplane onto an incorrect taxiway.
In addition to taxiing on the correct taxiways, it is important for crewmembers to recognize and stop their airplane at holdshort lines. A holdshort line is typically found at the intersection of a taxiway and a runway or at the intersection of a low-speed taxiway and a high-speed taxiway. A taxiing airplane should stop at each holdshort line until clearance is received from ground control to allow faster moving airplanes to pass.
It would be desirable to have a taxiing navigation system that would help ensure that the crewmembers of a taxiing airplane correctly receive the cleared taxi route, correctly follow that taxi route, and stop at holdshort lines as appropriate.